The Peruvian upwelling system is one of the most unpredictable but productive marine
ecosystems in the world that is regularly affected by El Nino and La Nina events. As a
consequence, South American sea lions (Otaria flavescens) inhabiting the Peruvian coast face
stochastic fluctuations in the abundance and distribution of their prey.
The goal of my study was to determine the effects of marine environmental changes on the
reproductive success of South American sea lions in Peru on the Ballestas Islands during the
1997-2002 breeding seasons. I also wanted to assess whether changes in diet and maternal
behaviour during this time were proxies of major changes in the abundance of marine
resources.
South American sea lions consumed primarily anchovy and squat lobster during the 1999-
2001 La Nina, but consumed a greater diversity of prey when abundance was low during the
1997-1998 El Nino. Lactating females also modified the length of time they spent at sea and
onshore in response to changes in the abundance of prey. Low abundances and quality of
prey during El Nino caused females to continue foraging for longer periods. This resulted in
greater times between nursing episodes, and ultimately led to the starvation of pups. In
contrast, during the 1999-2001 La Nina, females spent shorter times at sea and longer times
onshore as prey became more abundant.
Pup production and mortality were also directly related to the abundance of prey. Pup
mortality reached 100% during El Nino and remained high during the favourable conditions
of La Nina due to the short-term effects that El Nino had on population dynamics and
subsequent maternal behaviour. Abortions were also higher during El Nino compared to other
years, while numbers of pups bom were significantly reduced during and after El Nino due to
the death of a high proportion of the adult population.
My study suggests that South American sea lions in Peru are highly vulnerable to extreme
changes in prey abundance. It also demonstrates that sea lion reproductive parameters,
maternal attendance, and diet are strongly related to marine environmental conditions and
annual variations in prey abundance. As a result, South American sea lions appear to be good
indicators of stochastic changes in the distribution and abundance of marine resources in the
Peruvian upwelling ecosystem. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/16219 |
| Date | 05 1900 |
| Creators | Soto, Karim H. |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 4860650 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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